Safety arrangements for power machinery

ABSTRACT

A safety arrangement is disclosed for power machinery such as a folding machine ( 10 ) for sheet metal or plate ( 40 ). An operator is charged to a potential above that of the folding machine ( 10 ) through a foot pedal ( 20 ) and his potential is monitored by means of a control device ( 20   a ). If there is a drop in operator potential, machine cycles cannot be started and any cycle under way is halted or reversed. Safety gloves ( 28 ) are provided which are made of an electrically conductive material ( 28   a ) and onto which is integrated an insulating layer  28   c  over the palm ( 30   a ). The insulating layer ( 28   c ) allows handling of metal work pieces ( 40 ) without electrical contact being made with the folding machine ( 10 ). Meanwhile, the exposed nature of the conductive layer ( 28   a ) on the backhand ( 30   c ) ensures that the operator is protected from injury from machine parts ( 12, 14, 18 ) approaching the gloved hand ( 30 ) from the side not being used for work.

FIELD OF THE INVENTION

[0001] The present invention relates to safety arrangements for power machinery and in particular to safety arrangements for operator protection during the use of such machines.

BACKGROUND TO THE INVENTION

[0002] There are many power operated machines which can be dangerous to use due to the possibility of operator body parts being caught in a moving mechanism, between machine parts moving towards each other. Alternatively an operator can be injured in some other way related to the particular operating characteristics of the specific machine under consideration.

[0003] Prior art arrangements dealing with this problem are disclosed in EP 0362937 and EP0636830. Both of these documents describe an operator wearing two gloves, a conductive glove with an overlaying insulating glove. EP 0636830 describes an arrangement in Which operator safety for a meat processing (cutting) machine is considered. In this prior art arrangement, an operator wears conductive gloves and rests his feet on conductive plates, which are insulated from the ground. The machine itself is electrically connected to earth. An electrical current is passed through the operator's body. If the operator makes contact with an electrically conductive part of the machine, the current is short-circuited to earth and the machine is stopped or reversed.

[0004] The gloves are worn because the hands are in the most dangerous area of the operation and the conductivity of the gloves helps to ensure an easier path to earth for the current in the event of contact. In this manner, the proposal hopes to reduce the propagation delay between the initial contact and interference with the machine cycle.

[0005] The current is passed through the operator by his wearing electrically conductive footwear and standing with one foot on each of-a pair of conductive plates. A low-tension voltage (12-24V) is put across the plates and current is generated through the operator body, entering through one conductive shoe and exiting through the other.

[0006] One disadvantage of the manner in which current is passed in this prior art system is in the use of conductive plates, which require a more or less fixed operating stance with both feet in specific positions. This restricts operator freedom of movement and also places limits on where the operator may stand. For example, a long machine may require periodic movement of operator position along a working bed.

[0007] A problem can also be envisaged with the gloves of this prior art, which is acknowledged in the specification. When manipulating a work piece or material which is at least partially electrically conductive, in this case a piece of meat, the conductive nature of the gloves might cause the safety circuit to trip through the work piece. This same problem exists with other machines. For example, in the metal industry machines are used among other things for bending, folding, shearing and pressing sheets or sections of often very conductive material. Clearly using conductive gloves would prove problematic.

[0008] The solution offered in EP0636830 is to wear another pair of gloves, this time insulating, above the conductive gloves and rely on the outer insulating gloves to be torn away or their insulation compromised in some other way in the event of operator/machine contact so as to allow the short circuit through the then exposed conductive glove below.

[0009] One problem with the prior art solution is that an operator must remember to put on the outer insulating gloves and in any case the overall bulk of the resultant combination may restrict feel or movement. This solution may also prove less than satisfactory in some other ways and applications. If machines used in the metal industry as discussed above are considered, some of their moving parts may not be of such a nature as to tear away the outer insulating glove. For example, in a sheet metal folding machine, as in say a slow moving press, it can be envisaged that a compressive force might be applied to an unfortunately placed gloved hand. This could possibly crush the hand without exposing the conductive glove of EP0636830 and operator safety would thereby be compromised.

[0010] It is an object of the present invention to provide improved operator protection during the use of power machinery.

[0011] It is a further object of the present invention to provide apparatus and methods for improved operator protection during the use of power machinery.

SUMMARY OF THE INVENTION

[0012] Accordingly, the present invention provides a safety arrangement for a power operated machine. The safety arrangement includes a safety glove being worn in use by an operator of said machine and comprising a conductive layer, a charging device adapted to put a user wearing said glove at a different voltage potential with respect to one or more conductive parts of said machine and a control device adapted to monitor said potential and to substantially halt or reverse movement of a part of said machine in the event of a change in said potential indicative of contact between said user and at least one of the conductive parts. The glove further comprises an insulating layer integral with the conductive layer and extending over a working area of the glove. In a non-working area of the glove the level of insulation over the conductive layer is reduced compared to that in the working area to form a protection area, e.g. the non-working area has less thickness of insulation material compared to the working area, or protrusions of the conductive layer are formed towards the insulation layer in the non-working area to penetrate the insulating layer over the non-working area in case of a crushing accident. Alternatively, the conductive layer may be left exposed over a non-working area of the glove so as to form a protection area. This ensures that the operator is able to handle with said working area of the glove a work piece or material associated with said machine without making electrical contact with one of the said electrically conductive parts of said machine, and benefits from protection against contact with said machine over at least said protection area.

[0013] The safety glove may be made, according to a first embodiment, of a complete conductive glove, covered at the working area with an insulating material leaving the conductive layer exposed in the protection area. Alternatively, according to a second embodiment, it may be made of a complete insulating glove, covered at the non-working area with a conductive material. According to a third embodiment, it may be formed of two different parts, a conductive part and an insulating part. Alternatively, according to a fourth embodiment, it may be made of a complete insulating glove which covers completely a conductive material. In all embodiments, the conductive part and the insulating part are made integral with each other.

[0014] The insulating layer integral with the conductive layer may cover at least part of a palm and/or digit area. In one embodiment the insulating layer does not extend substantially onto a top surface of at least a backhand area of said glove to form a protection area. Hence, the protection area may cover at least part of an upper surface of the backhand and/or digit area of said glove. Said integral insulating layer may comprise any suitable material and is preferably flexible and hard wearing. In some applications it is preferably liquid impermeable. The insulating material may be at least one of a polyvinyl chloride material (PVC), an insulating elastomer such as a rubber material and a synthetic coating or resin. Said integral insulating layer may further comprise protection against mechanical injury to a gloved hand, for example by mechanical resistance to cuts from swarf or burrs on a work piece or machine part. Such protection may include, for instance, fibre reinforcements are additional protection plates attached to the surface. The conductive layer may comprise e.g. a textile such as any knitted, braided or woven or non-woven conductive material, for instance conductive textile material or steel wire. Preferably the conductive layer is flexible. The conductive layer does not need to be knitted. Alternatively the conductive layer may be a conductive coating, e.g. made of a conductive polymer such as conductive polyurethane.

[0015] Said charging device may comprise a foot operated machine control such as a switch or pedal which is adapted to apply a low tension voltage to an operator through a conductive piece of footwear, the operator being insulated from earth potential at his opposite foot. The low-tension voltage is preferably between 5 and 30 volts, most preferred about 12 volts. The conductive piece of footwear preferably comprises a sole formed of a special elastomer material of high electrical conductivity.

[0016] The operator may be insulated from earth potential by wearing insulating footwear on said opposite foot and/or by placing said opposite foot onto an insulating surface. The insulating piece of footwear preferably comprises a sole formed of an insulating elastomer material or a synthetic resin. A breakdown in insulation between said opposite foot and earth potential may be treated by said control device in the same manner as electrical contact between said operator and said machine.

[0017] Said foot operated control may include a sensing device for monitoring at least one of the resistance through said conductive piece of footwear, a current through a portion of said conductive footwear and a potential difference between said operator and said machine or earth potential.

[0018] Said control device may check authorisation of the operator to use said machine, may monitor for faulty footwear and may enable machine cycling only if both said checks pass. Said authorisation check comprises for example a resistance check through said conductive footwear.

[0019] Said control device may be operatively connected between said foot operated control and a cycle controller of said machine. It is optionally integrated with said foot operated control.

[0020] Said foot operated control may be moveable, for example by provision of a flying lead connection.

[0021] Said machine may be operated by co-operation between said foot operated control and a hand operated control, for example by enabling operation of said machine by means of said foot operated control and initialising an operating cycle by means of a hand control operated by the same operator using said foot control or by an associated operator.

[0022] Said charging device may be provided with a power supply galvanically separated and operationally independent of a machine cycle supply.

[0023] Said operator may be brought to said potential difference substantially only in an operating cycle of said machine during which cycle parts of said machine are moving, those moving parts preferably comprising user accessible parts. Said potential difference between said operator and said machine may be positive, for example +12 volts.

[0024] Said control device may determine a contact between said operator and said machine by a drop in the potential difference therebetween.

[0025] Said machine may comprise a machine in which parts move, preferably slowly, i.e. for example in the order of 15 cm/s or slower, preferably 10 cm/s or slower, towards each other in the region of a materials handling portion accessible to an operator, for example folding machines or cutting devices such as power shears.

[0026] The present invention also provides a method of operating power machinery and manipulating work pieces or material in association therewith, including:

[0027] a) wearing as an operator a safety glove comprising a conductive layer and an integral insulating layer, said insulating layer covering a working area of said glove such as for example a palm and or digit area and at least part of a further area of said glove has a reduced insulation level compared to the working area to form a protection area, e.g. substantially free of insulating material;

[0028] b) charging said operator to a voltage potential different from one or more conductive parts of said machine, preferably by means of a low tension voltage positive with respect to said machine parts;

[0029] c) monitoring said operator potential with respect to said machine parts and preferably also with respect to earth potential;

[0030] d) substantially halting and/ or reversing a machine cycle if said potential changes beyond a predetermined limit or falls to substantially zero with respect to said machine parts or earth potential.

[0031] The method may include charging said operator through an electrically conductive piece of footwear, said charging being supplied through a foot operated machine control, preferably in the form of a low tension voltage, and insulating the opposite foot of said operator.

[0032] The method may include insulating said operator by wearing non-conductive footwear on said opposite foot and/or placing said opposite foot on an insulating surface.

[0033] The method may include monitoring at least one of the resistance through a part of said conductive footwear, preferably a sole thereof, and a current through a portion of said conductive footwear.

[0034] The method may include charging said operator from a power supply substantially operationally independent of a machine cycle supply, said independent power supply being fed through said foot operated control.

[0035] The method may include charging said operator only in an operating cycle of said machine during which cycle parts of said machine are moving, those parts preferably comprising user accessible parts.

[0036] The present invention also provides a safety glove suitable for use in a safety arrangement or method according to the invention. Such a glove comprises a conductive layer and an integral insulating layer over a working area of said conductive layer, a non-working area of said conductive layer having a reduced insulation level compared with the insulation level over the working area. For example, the conductive layer in the protection area may be left exposed.

[0037] The safety glove may be made, according to a first embodiment, of a complete conductive glove, covered at the working area with an insulating material. Alternatively, according to a second embodiment, it may be made of a complete non-conductive glove, covered at the non-working area with a conductive material. According to a third embodiment, it may be formed of two different parts, a conductive part and an insulating part, which are integral with each other. Alternatively, according to a fourth embodiment, it may be made of a complete insulating glove which covers completely a conductive material. In all embodiments, the conductive part and the insulating part are made integral with each other.

[0038] Said integral insulating layer integral with the conductive layer may cover at least part of a palm and/or digit area. The insulating does not need to extend substantially onto at least a backhand area of said glove. Said protection area may cover at least part of an upper surface of the backhand and/or digit area of said glove. Said integral insulating layer may comprise a suitable insulating material which is preferably flexible and hard wearing. In some applications the insulating layer should be impermeable to liquids. The insulating material may be at least one of a polyvinyl chloride material (PVC), an insulating elastomer such as a rubber material and a synthetic coating or resin. Said integral insulating layer may further comprise protection against mechanical injury to a gloved hand, for example by mechanical resistance to cuts in use from swarf or burrs on a work piece or a machine part. Such a resistance may be provided by embedded fibre reinforcements or plates attached to its surface. The conductive layer may comprise a flexible conductive layer especially a conductive textile, e.g. any knitted, braided, woven or non-woven conductive material, such as conductive textile material or steel wire. The conductive layer does not, however, need to be knitted.

[0039] The present invention further provides safety footwear for use in an arrangement or method according to the invention or in conjunction with a glove according to the invention. The footwear comprises a pair of footwear in which each piece of the pair has a different electrical conductivity, preferably one piece being electrically conductive and the other piece being electrically insulating.

BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The present invention will now be described by way of example only and with reference to the accompanying drawings, in which:

[0041]FIG. 1 is a schematic diagram of a safety arrangement for power machinery according to an embodiment of the present invention; and

[0042]FIG. 2 is a drawing of a palm view and a backhand view of a safety glove used in the arrangement of FIG. 1.

[0043]FIG. 3A is a cross-sectional view of an embodiment of an upper body of a power machine comprising an upper part and an intermediate part attached to each other by means of an intermediate part. FIG. 3B is a detailed elevational view of the intermediate part as represented in FIG. 3A, the intermediate part being provided with movement means for moving separate units of the intermediate part towards or away from each other.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0044] The present invention will be described with reference to certain embodiments and drawings but these provide only examples of the invention. The skilled person will appreciate that there are a variety of ways implementing the invention within the scope of the attached claims, all such alternative embodiments also being within the scope of the present invention;

[0045] Referring to the figures, a safety arrangement is provided for a power machine which, in the illustrated embodiment, comprises e.g. a metal folding machine 10 for materials and work pieces such as sheet metal or plate 40.

[0046] The folding machine 10 comprises lower and upper bodies 12, 14 which move slowly towards each other, e.g. at a speed between 10 cm/s and 13 cm/s, to clamp a work piece 40 between them. A machine cycle controller 16 controls a motor (not shown separately) which moves a machine part in the form of a pivoting jaw 18 so as to fold the work piece 40 upwardly in the direction of the arrow 18 a and back downward to the rest position after a fold of the desired nature has been applied to the work piece 40. In the illustrated embodiment, the folding machine 10 has been set-up for illustrative purposes only such that the maximum fold is a right angle, generated by pivoting the jaw 18 until the work piece 40 comes up against a limit surface 14 a of the upper body 14. It will be appreciated by those familiar with this sort of machine that intermediate folds and other folding configurations can be employed.

[0047] The work piece 40, lower and upper bodies. 12, 14 and the pivoting jaw 18 are all metal, as is the limit surface 14 a, and therefore all are electrically conductive. The metal parts of the machine are earthed through the cycle controller 16 and by earth cables to earth potential E. Particular attention is paid to machine parts which move and especially those in user accessible positions.

[0048] An operator inserts, removes and manipulates work pieces 40 using one or both hands 30. For protection, the operator wears a safety glove 28, which, according to one embodiment, comprises a conductive layer 28 a, e.g. a conductive glove of the supplier ANSSELL n.v., located in Aalst, Belgium, for example type HYFLEX 11-620. The conductive layer of each glove 28 then defines a cavity 28 b into which in use the appropriate operator hand 30 is inserted.

[0049] Each glove 28 further comprises an integral insulating layer 28 c, made from an insulating material such as polyvinyl chloride (PVC) or a suitable insulating elastomer such as rubber or a synthetic resin or coating. Preferably, a silicone 3481 obtainable from Dow Corning is used. The insulating layer 28 c is integrated with the conductive layer 28 a by any suitable method, such as e.g. bonding, over-moulding, immersing, spraying, etc. For example a conductive glove may be pulled over a pre-formed hand, after which this pre-formed hand with glove is put in a mould, which reveals only one side of the glove. The revealed side of the glove is then covered with an insulating polymer, for example by spraying. By the presence of the mould, the insulating polymer cannot be applied onto the non-revealed side of the glove, and the insulating and conductive parts on the glove have a neat dividing line. An alternative possibility is to apply, for example by gluing, a piece of polymer which is previously cut to measure. This method also provides a nice dividing line between the insulating and the conductive part of the glove.

[0050] The insulating layer 28 c is applied over a working area of the glove 28, i.e. the area of each glove 28 normally used to handle and contact work pieces 40. To achieve this, the insulating layer 28 c preferably covers at least the majority of the palm area 30 a and preferably also the underside part of each digit 30 b. The insulating layer 28 c preferably also provides protection to an operator from mechanical injury from the likes of swarf or burrs either on the work piece 40 or on the folding machine 10 itself. The protection may be provided by mechanical resistance of the insulating layer 28 c to cuts or tears.

[0051] The insulating layer 28 c does not extend at all, or at least not very far, onto the backhand 30 c of the glove 28, the backhand 30 c preferably being considered also to include the upper surface of the digits 30 b. In this way, the conductive layer 28 a is left exposed over substantially all the surface area of the glove 28 not normally used to handle or make contact with work pieces 40 and referred to for convenience as a non-working area of the gloved hand 28, 30. The exposed conductive layer 28 a over the non-working area of the glove 28 forms a protection area, as will be discussed in further detail below.

[0052] A charging device is provided to put the operator at a different voltage potential with respect to the conductive parts 12, 14, 14 a, 18 of the folding machine 10. The charging device is incorporated as part of a safety monitoring and control circuit 20 a associated with a foot operated machine control in the form of foot switch/pedal 20, and supplies the potential to the operator from a power supply 22 which is operatively separated from the power supply 16 a to the folding machine 10 being controlled. The operator is raised to a positive potential of between 5 and 30 volts, preferably about 12 volts above that of the normal grounded state of the folding machine 10. It will be appreciated that other potential differences could be employed in dependence on application specific circumstances. In order to keep to a minimum the amount of time an operator is kept under charge, charging preferably only occurs during a machine cycle in which parts 12, 14, 18 of the folding machine 10 which are user accessible are moving.

[0053] The pedal 20 is preferably moveable, for example by connection to the cycle controller 16 using a flying lead. This improves flexibility of the arrangement over those arrangements, which call for foot controls in fixed positions by, for example, allowing an operator to move the work area along or around the folding machine 10. It is also possible for operators to work in teams with, for example, a second operator initialising an operating cycle using a hand control 32, which will only take place if the charged operator passes the safety checks described below.

[0054] The monitoring and control circuit 20 a further co-operates with a sensing device in the form of a pair of sensors 20 b which are integrated with the pedal 20 and spaced apart towards opposite ends of the operator's conductive footwear 24. The sensors 20 b and the monitoring and control circuit 20 a perform safety checks of the authorisation/competence of the operator to use the machine, check for faulty footwear 24 and monitor the potential of the operator. The monitoring and control circuit 20 a may be incorporated in the pedal 20 or may be a separate unit operatively connected between the foot pedal 28 and the cycle controller 16.

[0055] Operator authorisation is checked by a resistance and/or current check through the sole of the conductive footwear 24, and the same test checks for faulty footwear, which will fail the test in the same way as footwear with the wrong resistance. If the potential difference of the operator drops e.g. 50% or less, preferably 20% or less, or is not within tolerance with respect to the folding machine 10, the monitoring and control circuit 20 a does not send a cycle enable signal to the cycle controller 16 and, if a cycle has already been started, sends an emergency signal to the cycle controller 16 which halts and/or reverses the cycle. It can therefore be seen that electrical contact between the operator and the folding machine 10 or earth potential prevents, stops and/or reverses machine cycling. The operator cannot therefore practically work the folding machine 10 without wearing the safety gloves 28 and a cycle is only enabled if both the authorisation and safety checks pass.

[0056] For the conductive footwear 24, preferably an electrically conductive shoe is used with an electrical resistance between 200 kΩ and 1 MΩ. Such a shoe can e.g. be found on the market under the tradename EMMA from supplier EMMA, located in the Netherlands.

[0057] To ensure the operator does not short circuit the potential difference to earth E through his opposite leg 26 a, an insulating piece of foot wear 26 is worn on the foot opposite to the one used to operate the pedal 20. A breakdown in insulation of the insulating footwear 26 will have the same effects, and be treated in the same manner as, contact between the operator and the folding machine 10.

[0058] In the alternative to providing a pair of footwear having different electrical conductivity 24, 26, a pair of conductive foot wear 24, 24 could be worm, but in that case it would prove necessary to make sure that the operators opposite foot 26 a was placed on an insulating surface during folding cycles or otherwise isolated from earth potential E. This would, however, give the operator the choice of which foot 24 a, 26 a to use to enable folding cycles.

[0059] A person skilled in the art can easily provide a monitoring and control circuit 20 a based on standard electronics. It may be based on a FET transistor as a measurement instrument. The circuit 20 a can also be built with an operational amplifier or a transistor. Even a high frequency signal can be used, either on the machine or on the operator, with which switching takes place at the moment of changing this signal.

[0060] To perform a folding cycle, the operator first manipulates or places a work piece 40 in a clamped position between the lower and upper bodies 12, 14 of the metal folding machine 10. Next, an operating cycle is enabled by the operator pressing the pedal 20 using the foot 24 a wearing the conductive footwear 24. The monitoring and control circuit 20 a measures between the sensors in the pedal 20 whether the resistance in the conductive footwear 24 is low enough. If so, a timer is set which is in an ON position during e.g. 3 seconds, and during that time period it is checked by the monitoring and control circuit 20 a whether a contact (conductive path) exists between the operator (the conductive part of the glove) and the sensors in the pedal 20. If not, a cycle enable signal is sent to the cycle controller 16, otherwise no cycle enable signal is sent. The operator then presses a hand control in the form of a cycle start button 32 and, if the cycle controller 16 has received a cycle enable signal from the monitoring and control circuit 20 a, the cycle will be performed and the jaw 18 will move in the direction of arrow 18 a to fold the work piece 40. This way, for every cycle it is checked whether an authorised person is running the machine, and whether or not he/she is in a dangerous position.

[0061] Using the above arrangement, an operator can handle work pieces 40 with the working area 28 c of the glove, even if the work piece 40 is electrically conductive and comes into electrical contact with a metal part of the folding machine 10. The protection area of exposed conductive layer 28 a provides protection against injury by short circuiting the operator potential to earth E if any of that part of the gloved hand 30 comes into contact with a metal part 12, 14, 14 a, 18 of the folding machine 10.

[0062] There is no propagation or reaction delay as would be the case if the backhand 30 c were to be well insulated, such as would be the case if the operator were to be wearing an insulating pair of gloves over a conductive pair and had to wait for the insulation to be breached before an emergency signal could be sent to stop and/or reverse the machine. It will be noted, of course, that such a breach may not even happen in a crushing accident of the type which might be expected in a machine such as a metal folding machine 10. In addition, through the integral nature of the insulating layer 28, the operator retains the sensitivity of an apparently single skinned pair of gloves 28 and doesn't suffer from, for example, loss of control, feel or dexterity as might happen during relative movement between gloves in a two glove per hand arrangement.

[0063] In order to deal with inertia of some heavier and faster machines (those machines which have a concourse larger than 2 mm, which means that they still move 2 mm further after the forward drive has been switched off), the upper body 14 may be formed by an upper body 14 comprising an upper part 14 a and a lower part or tool 14 b fixed to each other by means of an intermediate part 14 c, as shown in FIG. 3A. This intermediate part 14 c consists of two massive parts 15 a, 15 b which fit to each other, for example by means of a V-shape, as shown in FIG. 3B. Both parts 15 a, 15 b are connected to each other by means of movement devices, such as for example small hydraulic cylinders 50. These hydraulic cylinders 50 are actuated together with the actuation of the machine (actuation means for the hydraulic cylinders 50 or connections thereto are not represented in FIG. 3B). This means that if the upper body 14 moves towards the lower body 12 (upper body 14 moves down), then part 15 b moves away from part 15 a (part 15 b moves down more than part 15 a) by means of hydraulic cylinders 50. If the upper body 14 moves away from the lower body 12 (upper body 14 moves up), then part 15 b moves towards part 15 a by means of the hydraulic cylinders 50. If a dangerous contact is made, i.e. for example the conductive part of a glove worn by an operator touches a metallic part of the machine, the machine is halted and/or reversed, which means that the upper body 14 does not move any longer towards the lower body 12. At the same time, the hydraulic cylinders 50 are actuated so as to make part 15 b move towards part 15 a. Parts 14 b and 15 b are much smaller than upper body 14 in its entirety, and therefore suffer less from inertia. Therefore parts 14 b and 15 b can move up faster, and thus the total concourse will be smaller than the concourse when the upper body 14 consisted of one single piece.

[0064] A further embodiment of the glove used in the present invention will be described. In this embodiment the insulating layer 28 c is applied not only over a working area of the glove 28, i.e. the area of each glove 28 normally used to handle and contact work pieces 40 but also over other non-working areas of the glove, e.g. the backhand. To achieve this, the insulating layer 28 c extends beyond the majority of the palm area 30 a and preferably also the underside part of each digit 30 b. The insulating layer 28 c preferably also provides protection to an operator from mechanical injury from the likes of swarf or burrs either on the work piece 40 or on the folding machine 10 itself. The protection may be provided by mechanical resistance of the insulating layer 28 c to cuts or tears.

[0065] In this embodiment the insulating layer 28 c can extend onto the backhand 30 c of the glove 28, the backhand 30 c preferably being considered also to include the upper surface of the digits 30 b. In this way, the conductive layer 28 a is not left exposed over substantially all the surface area of the glove 28 not normally used to handle or make contact with work pieces 40 and referred to for convenience as a non-working area of the gloved hand 28, 30. Without further modification this glove does not react quickly to a crushing accident. To provide additional protection the insulation level in the non-working area is reduced compared to the working area. This reduction in insulation level can be achieved for instance by reducing the insulation thickness to a level below that used in the working area. Another method is to provide protrusions on the outer surface of the conductive layer such as spikes directed towards the insulating material so that on crushing pressure these penetrate through the insulating layer and activate the machine stopping procedure. In this embodiment a trade-off is made between protection of the operator and preventing accidental machine stoppages by accidental contact with the exposed conductive layer.

[0066] From the above it will be appreciated that in a first aspect of the present invention a safety arrangement for a power operated machine 10 is provided. Said safety arrangement includes a safety glove 28 being worn in use by an operator of said machine and comprising a conductive layer 28 a, a charging device adapted to put a user wearing said glove at a different voltage potential with respect to one or more conductive parts 12, 14, 18 of said machine and a control device 20 a adapted to monitor said potential indicative of contact between said user and a said conductive part. Said glove 28 further comprises an integral insulating layer 28 c over a working area of said glove. An insulation level over the conductive layer 28 a is reduced over a non-working area of said glove so as to form a protection area. For example, the conductive layer is exposed in this region. Said operator is able to handle with said working area a work piece or material associated with said machine without making electrical contact with a said electrically conductive part of said machine and benefits from protection against contact with said machine over at least said protection area. In this first aspect said integral insulating layer 28 c can cover at least part of a palm and/or digit area 30 a and does not need to extend substantially onto at least a backhand area 30 c of said glove 28, Said protection area can cover at least part of an upper surface of the backhand and/or digit area 30 c of said glove 28. In this first aspect said integral insulating layer 28 c can comprise any suitable insulating material. The material is preferably flexible and supple. In some applications it can be impermeable to liquids. It may be at least one of a polyvinyl chloride material (PVC) and insulating elastomer such as a rubber material. In this first aspect said integral insulating layer 28 c can further comprise protection against mechanical injury to a gloved hand, for example by mechanical resistance to cuts from swarf or burrs on a work piece or machine part. In this first aspect said conductive layer 28 a can comprise any flexible conductive material, e.g. one of conductive textile material or steel wire. In this first aspect said charging device can comprise a foot operated machine control 20 which is adapted to apply a low tension voltage to an operator through a conductive piece of footwear 24, the operator being insulated from earth potential (E) at his opposite foot. Said operator can be insulated from earth potential (E) by wearing insulating footwear 26 on said opposite foot and/or by placing said opposite foot onto an insulating surface. A breakdown in insulation between said opposite foot 26 a and earth potential (E) can be treated by said control device 20 a in the same manner as electrical contact between said operator and said machine 10. In the above aspect said charging device 20 can include a sensing device 20 b for monitoring at least one of the resistance through said conductive piece of footwear 24, a current through a portion of said conductive footwear and a potential difference between said operator and said machine 10 or earth potential (E). In the above aspect said control device 20 a can check authorisation of the operator to use said machine 10, monitors for faulty footwear 24, 26 and enables machine cycling only if both said checks pass. In the above aspect said control device 20 a can be operatively connected between said foot operated control 20 and a cycle controller 16 of said machine 10 and is optionally integrated with said foot operated control. Inn the above aspect said foot operated control 20 is moveable. In the first aspect said machine 10 can be operated by co-operation between said foot operated control 20 and a hand operated control 32. In the first aspect said charging device can be provided with a power supply 22 operationally independent of a machine cycle supply. In the first aspect said operator can be brought to said potential difference substantially only in an operating cycle of said machine 10 during which cycle parts 12, 14, 18 of said machine are moving, those moving parts preferably comprising user accessible parts. In the first aspect said potential difference between said operator and said machine 10 can be positive. In the first aspect said control device 20 a determines a contact between said operator and said machine 10 by a drop in said potential difference therebetween. In the first aspect said machine 10 comprises a machine in which parts 12, 14, 18 move towards each other in the region of a materials handling portion accessible to a said operator.

[0067] In a second aspect of the present invention a method of operating power machinery 10 and manipulating work pieces or material 40 in association therewith, is provided including a) wearing as an operator a safety glove 28 comprising a conductive layer 28 a and an integral insulating layer 28 c, said insulating layer covering a working area of said glove and the glove having at least part of a further area 30 c of said glove over which the level of insulation is reduced, e.g. is substantially free of insulating material; b) charging said operator to a voltage potential different from one or more conductive parts of said machine, preferably by means of a voltage positive with respect to said machine parts; c) monitoring said operator potential with respect to said machine parts and preferably also with respect to earth potential (E).

[0068] The second aspect can include charging said operator through an electrically conductive piece of footwear 24, said charging being supplied through a foot operated machine control 20, preferably in the form of a low tension voltage, and insulating 26 the opposite foot 26 a of said operator. The above method can include insulating said operator by wearing non-conductive footwear 26 on said opposite foot 26 a and/or placing said opposite foot on an insulating surface. The above method can include monitoring at least one of the resistance through a part of said conductive footwear 24, preferably a sole thereof, and a current through a portion of said conductive footwear. The second aspect can include charging said operator from a power supply 22 substantially operationally independent of a machine cycle supply, said independent power supply being fed through said foot operated control 20. The second aspect can include charging said operator only in an operating cycle of said machine 10 during which cycle parts 12, 14, 18 of said machine are moving, those parts preferably comprising user accessible parts.

[0069] In a third aspect of the present invention a safety glove 28 suitable for use in a safety arrangement according to aspect 1 is provided or in a method according to aspect 2, said glove comprising a conductive layer 28 a and an integral insulating layer 28 a over a working area of said conductive layer, a non-working area of said conductive layer having a reduced insulation level to form a protection area, e.g. the conductive layer is left exposed. Said integral insulating layer 28 c can cover at least part of a palm and/or digit area 30 a and does not need to extend substantially onto et least a backhand area 30 c of said glove. In the third aspect said protection area can cover at least part of an upper surface of the backhand and/or digit area 30 c of said glove. In the third aspect said integral insulating layer 28 c can comprise any suitable insulating material. The material is preferably flexible and hard wearing. In some applications it should be liquid impermeable. The insulating material may be at least one of a polyvinyl chloride material (PVC) and insulating elastomer such as a rubber material. In the third aspect said integral insulating layer 28 c further comprises protection against mechanical injury to a gloved hand. In the third aspect said conductive layer 28 a can comprise any flexible conductive material, e.g. a conductive textile material such as knitted, woven, braided or non-woven textiles comprising metal fibres, or steel wire.

[0070] In a fourth aspect of the present invention safety footwear 24, 26 is provided for use in an arrangement according to aspect 1, in a method according to aspect 2 or in conjunction with a glove 28 according to aspect 3, said footwear 24, 26 comprising a pair of footwear in which each piece of the pair has a different electrical conductivity, preferably one piece being electrically conductive 24 and the other piece being electrically insulating 26.

[0071] While the present invention has been shown and described with reference to preferred embodiments, it will be understood by those skilled in the art that various changes or modifications in form and detail may be made without departing from the scope and spirit of this invention. For example, it will be appreciated that the present invention is applicable to many power operated machines and in particular to those in which electrically conductive parts move at least slowly towards each other in a materials handling portion accessible to an operator. Examples beyond the power folding machine 10 discussed above include for example power shears and at least slow moving presses. 

1-22. (cancelled)
 23. a safety arrangement for a power operated machine (10), said safety arrangement including a safety glove (28) being worn in use by an operator of said machine and comprising a conductive layer (28 a), a charging device adapted to put a user wearing said glove at a different voltage potential with respect to one or more conductive parts (12, 14, 18) of said machine and a control device (20 a) adapted to monitor said potential and to substantially halt or reverse movement of a part of said machine in the event of a change in said potential indicative of contact between said user and a said conductive part, characterised in that said glove (28) further comprises an insulating layer (28 c) over at least a working area of said glove, said insulating layer being integral with said conductive layer, a level of insulation over a non-working area of said glove being lower than over the working area of said glove so as to form a protection area, whereby said operator is able to handle with said working area a work piece or material associated with said machine without making electrical contact with a said electrically conductive part of said machine:
 24. A safety arrangement according to claim 23, wherein an area of part of the conductive layer at the non-working area is exposed and the operator benefits from protection against contact with said machine over at least said exposed area.
 25. A safety arrangement according to claim 23, wherein said integral insulating layer (28 c) covers at least part of a palm and/or digit area (30 a) and does not extend substantially onto at least a backhand area (30 c) of said glove (28).
 26. A safety arrangement according to claim 23, wherein said protection area covers at least part of an upper surface of the backhand and/or digit area (30 c) of said glove (28).
 27. A safety arrangement according to claim 23, wherein said conductive layer (28 a) comprises any of conductive textile material or steel wire.
 28. A safety arrangement according to claim 23, wherein said charging device comprises a foot operated machine control (20) which is adapted to apply a low tension voltage to an operator through a conductive piece of footwear (24), the operator being insulated from earth potential (E) at his opposite foot.
 29. A safety arrangement according to claim 28, wherein said operator is insulated from earth potential (E) by wearing insulating footwear (26) on said opposite foot and/or by placing said opposite foot onto an insulating surface.
 30. A safety arrangement according to claim 28, wherein said charging device (20) includes sensing device (20 b) for monitoring at least one of the resistance through said conductive piece of footwear (24), a current through a portion of said conductive footwear and a potential difference between said operator and said machine (10) or earth potential (E).
 31. A safety arrangement according to claim 28, wherein said control device (20 a) checks authorisation of the operator to use said machine (10), monitors for faulty footwear (24, 26) and enables machine cycling only if both said checks pass.
 32. A safety arrangement according to claim 28, wherein said control device (20 a) is operatively connected between said foot operated control (20) and a cycle controller (16) of said machine (10) and is optionally integrated with said foot operated control.
 33. A safety arrangement according to claim 23, wherein said operator is brought to said potential difference substantially only in an operating cycle of said machine (10) during which cycle parts (12, 14, 18) of said machine are moving, those moving parts preferably comprising user accessible parts.
 34. A safety arrangement according to claim 23, wherein said control device (20 a) determines a contact between said operator and said machine (10) by a drop in said potential difference therebetween.
 35. A method of operating power machinery (10) and manipulating work pieces or material (40) in association therewith, including a) wearing as an operator a safety glove (28) comprising a conductive layer (28 a) and an insulating layer (28 c) integral with said conductive layer, said insulating layer covering a working area of said glove and the glove having at least part of a further area (30 c) having a lower level of insulation than over the working area; b) providing a device for charging said operator to a voltage potential different from one or more conductive parts of said machine, preferably by means of a voltage positive with respect to said machine parts; c) monitoring said operator potential with respect to said machine parts and preferably also with respect to earth potential (E); d) substantially halting and/or reversing a machine cycle if said potential changes beyond a predetermined limit or falls to substantially zero with respect to said machine parts or earth potential.
 36. A method according to claim 35, wherein said device for charging includes means for charging said operator through an electrically conductive piece of footwear (24), said means for charging being adapted to supply through a foot operated machine control (20), preferably in the form of a low tension voltage, and providing means for insulating (26) the opposite foot (26 a) of said operator.
 37. A method according to claim 37, including means for insulating said operator includes a non-conductive footwear (26) for use on said opposite foot (26 a) of the operator and/or providing an insulating surface on which said opposite foot of an operator can be placed.
 38. A method according to claim 35, including monitoring at least one of the resistance through a part of said conductive footwear (24), preferably a sole thereof, and a current through a portion of said conductive footwear.
 39. A method according to claim 35, including operating said means for charging said operator only in an operating cycle of said machine (10) during which cycle parts (12, 14, 18) of said machine are moving, those parts preferably comprising user accessible parts.
 40. A safety glove (28) suitable for use in a safety arrangement according to claim 23, said glove comprising a conductive layer (28 a) and an insulating layer (28 a) over a working area of said conductive layer, said insulating layer being integral with said conductive layer, a non-working area of said conductive layer being having a lower level of insulation than over the working area to form a protection area.
 41. A glove (28) according to claim 40, wherein said integral insulating layer (28 c) covers at least part of a palm and/or digit area (30 a) and does not extend substantially onto at least a backhand area (30 c) of said glove to form an area in which the conductive layer is exposed.
 42. A glove (28) according to claim 40, wherein said protection area covers at least part of an upper surface of the backhand and/or digit area (30 c) of said glove.
 43. A glove according to claim 40, wherein said conductive layer (28 a) comprises any of conductive textile material or steel wire.
 44. A safety glove (28) suitable for use in a method according to claim 35, said glove comprising a conductive layer (2 a) and an insulating layer (28 a) over a working area of said conductive layer, said insulating layer being integral with saiduconductive layer, a non-working area of said conductive layer being having a lower level of insulation than over the working area to form a protection area.
 45. Safety footwear (24, 26) for use in an arrangement according to claim 23, said footwear (24, 26) comprising a pair of footwear in which each piece of the pair has a different electrical conductivity, preferably one piece being electrically conductive (24) and the other piece being electrically insulating (26).
 46. Safety footwear (24, 26) for use in a method according to claim 35, said footwear (24, 26) comprising a pair of footwear in which each piece of the pair has a different electrical conductivity, preferably one piece being electrically conductive (24) and the other piece being electrically insulating (26).
 47. Safety footwear (24, 26) for use in conjunction with a glove (28) according to claim 40, said footwear (24, 26) comprising a pair of footwear in which each piece of the pair has a different electrical conductivity, preferably one piece being electrically conductive (24) and the other piece being electrically insulating (26). 